Merge V8 at r10375: Roll to 3.6.6.17

Bug: 5688872
Change-Id: I558f9b89a15d2dcf1b62dcf9f297d4d42ca5830c
diff --git a/src/v8threads.h b/src/v8threads.h
index 4002bb3..a2aee4e 100644
--- a/src/v8threads.h
+++ b/src/v8threads.h
@@ -72,7 +72,7 @@
 };
 
 
-// Defined in top.h
+// Defined in isolate.h.
 class ThreadLocalTop;